Rear loading refuse vehicles are well known and are widely employed to transport municipal waste, for example. Generally, such vehicles employ an internal compartment, integral with a tailgate assembly, into which waste is deposited. The waste is then transferred into a main storage compartment and is compressed to economize on space. The system is typically integral with a purpose-built vehicle, although it may also be independently mounted to a truck chassis. The systems as described in some patents, such as U.S. Pat. Nos. 3,746,192, 3,777,917 and 4,029,224 (each of Herpich et al.), and U.S. Pat. No. 6,234,739 (Smith et al.), have improved upon the efficiency and durability of packing mechanisms by altering the placement of the hydraulic cylinders that mobilize the packing blade. Other improvements to rear loading refuse vehicles include positioning of the packing blade to avoid obstruction of the refuse deposited in the hopper, as in U.S. Pat. No. 4,460,307 (Durant et al.) and improved safety features such as those disclosed in U.S. Pat. No. 4,065,008 (Ratledge).
With the advent of recycling of municipal waste, it has become important to separate the waste stream, for example into “dry” and “wet” waste.
It is thus known to separate the refuse storage area of the main compartment into multiple sub-compartments to hold different waste materials. For example, each of U.S. Pat. No. 4,242,953 (St. Gelais), U.S. Pat. No. 4,113,125 (Schiller) and U.S. Pat. No. 5,123,801 (O'Daniel) disclose refuse vehicles with more than one storage compartment, with the compartments being aligned side by side. St. Gelais' truck has two compartments, one of which is served by a scraper blade, the other of which is packed by a press panel or ram. Schiller's refuse collecting system contemplates a separate feed or loading shovel for each separate chamber. Finally, O'Daniel's vehicle employs multiple scraper blades that empty the multiple buckets that receive refuse.
Multiple compartments may also aligned so that one compartment is above the other. U.S. Pat. No. 5,885,049 (McNeilus et al.) depicts a multiple compartment refuse vehicle in which one compartment is above the second compartment. The hopper has a lower and upper portion each of which is served by a separate packing mechanism.
Vehicles that employ multiple compartments for storing refuse have some limitations. For example, the viability of such vehicles is contingent upon the waste collection programmes and methods of public authorities. Different jurisdictions may have different waste separation and collection regimes such that a multi-compartmented vehicle may be suitable for one jurisdiction but not for its neighbour. Furthermore, the use of a separate packing mechanism to compress refuse in each separate compartment presents numerous disadvantages. First, if there are multiple tailgates and packing mechanisms, it is necessary to employ multiple power sources and components to operate those mechanisms. This increases the mass of the vehicle and thus diminishes its fuel efficiency. It also causes imbalance, since the packing components are located behind the rear wheels of the vehicle. Furthermore, the addition of more packers necessitates more frequent maintenance and thus makes the vehicle more expensive to build and operate. Finally, the individual packing mechanisms have less compaction capacity when there are multiple compacting means. Multiple packers are less efficient and thus the vehicles have less compaction capacity than traditional refuse transporting vehicles, known as “single stream” vehicles. As a result, such vehicles haul less trash than single stream vehicles with vehicle bodies having identical volumes.
Finally, the provision of a separate storage compartment to hold “wet” waste leads to other requirements. For example, as the compostable waste is compacted, it loses its water, thus creating liquid waste. This waste frequently escapes the refuse vehicle and presents an environmental hazard.
Once a number of loads of refuse have been transferred from the waste collection sub-compartments into the waste storage sub-compartments, the waste storage sub-compartments must have waste ejected from them. This can be achieved using rams or reciprocating slat-type conveyors.
Reciprocating slat-type conveyors are also known in the art for discharging refuse from a garbage truck. This type of conveyor system provides a convenient method of discharging refuse (or other loads) rearwardly from a trailer or container without tilting the trailer or utilizing rams with hydraulic extensions. The system typically includes a plurality of moveable slats extending lengthwise at the base of the trash compartment. The slats are independently driven with three or more drive means in a forward and rearward direction such that at any given moment either all slats or every third slat is in movement. Thus, a relatively short reciprocating movement will displace over time the entire load out of the trailer in a stepwise movement. Examples of such conveyors are disclosed in U.S. Pat. No. 4,143,760 (Hallstrom), U.S. Pat. No. 4,184,587 (Hallstrom), U.S. Pat. No. 4,691,819 (Hallstrom), U.S. Pat. No. 4,709,805 (Foster) and U.S. Pat. No. 5,934,445 (Foster et al.).
When the loads transported by a vehicle contain a liquid component, liquid may seep onto conveyor slats, between conveyor slats onto the drive means and out of the trailer or vehicle onto the road. This is especially problematic when the load is refuse such that the liquid may be toxic and its escape from the trailer or vehicle contravenes environmental regulations. Various solutions have been proposed in response to the seepage of toxic liquids from the load. U.S. Pat. No. 6,013,585 (Foster et al.) describes a method for manufacturing conveyor slats that are chemical resistant and non-corrosive. Each of U.S. Pat. No. 5,165,525 (Quaeck), U.S. Pat. No. 5,267,641 (Hallstrom, Jr.) and U.S. Pat. No. 5,547,067 (Foster) disclose base members to which the conveyor slats are attached. The base members may be attached, configured or sealed in such a manner so as to prevent the leakage of liquid beneath them. U.S. Pat. No. 5,088,595 and RE35,156 each disclose a liquid receptacle that collects liquid. The liquid receptacle extends beneath a portion of each base member.
Reciprocating conveyors may be attached to frameless trailers, as described in U.S. Pat. No. 5,957,267 (Quaeck et al.). Frameless trailers minimize the total mass of the load by eliminating components of the conventional framework assembly that normally supports the load. One drawback associated with the use of a frameless trailer is the damage sustained by the piston rods, which are components of the drive means, when loads are dropped on the conveyor slats above the piston rods. U.S. Pat. No. 5,957,267 adds fixtures to the drive means assembly, which fixtures bear the loads that are dropped upon the conveyor slats.
A further limitation that has been identified in prior art reciprocating conveyors is the position of the drive means. When such reciprocating conveyors are not fitted with base members, liquid waste seeps onto the drive means located beneath the conveyor slats, thus hampering movement of the conveyor slats. In liquid impermeable conveyor systems, it is expensive and labour intensive to mount a drive means below the conveyor slats. This is because an extensive hose and tubing system is necessary to connect the hydraulic fluid supply that is frequently a component of such drive means to drive units such as pistons. Thus U.S. Pat. No. 5,222,590 (Quaeck) discloses a configuration in which the drive means is positioned outside of the container in which the load is transported.
There are a number of limitations associated with prior art reciprocating conveyors, including improved reciprocating conveyors adapted to transport loads having a liquid component. Adding seals to each base member increases the costs of manufacture. Using base members to prevent the leakage of liquid beneath them is undesirable because such base members are susceptible to damage from the impact that they sustain when loads are dropped upon them. Replacing such base members is more costly and time-consuming when they are sealed. Furthermore, changing the configuration of the slats when they have a complicated base member structure, whether or not such structure includes seals, is also costly and time-consuming. Moreover, such seals trap moisture amongst the base member structure, thus making it susceptible to damage from the freezing of such moisture in cold temperatures. Finally, previous means for preventing leakage through the conveyor could not be attached to the conveyors of more than one manufacturer, since the width of the conveyor slats varies depending on who manufactures them.